Among viruses, human immunodeficiency virus (HIV), a kind of retrovirus, is known to cause acquired immunodeficiency syndrome (AIDS). The therapeutic agent for AIDS is mainly selected from a group of reverse transcriptase inhibitors (e.g., AZT, 3TC) and protease inhibitors (e.g., Indinavir), but they are proved to be accompanied by side effects such as nephropathy and the emergence of resistant viruses. Thus, the development of anti-HIV agents having the other mechanism of action has been desired.
On the other hand, a multidrug combination therapy is reported to be efficient in treatment for acquired immunodeficiency syndrome (AIDS) because of the frequent emergence of the resistant mutant. Reverse transcriptase inhibitors and protease inhibitors are clinically used as an anti-HIV agent, however agents having the same mechanism of action often exhibit cross-resistance or only an additional activity. Therefore, anti-HIV agents having the other mechanism of action are desired.
As a compound having inhibitory activity against HIV integrase, 1,6-naphthyridine derivative is known (see Patent documents 1 to 7). The derivative has a cyclic group such as aryl or heteroaryl at 7-position of side chain end.
Also a 1,6-naphthyridine derivative having a similar structure to the compound of the present invention was internationally filed by the present applicant (see Patent document 8).    [Patent document 1]    WO 2002/30426    [Patent document 2]    WO 2002/30930    [Patent document 3]    WO 2002/30931    [Patent document 4]    WO 2002/36734    [Patent document 5]    WO 2002/44079    [Patent document 6]    WO2003/77850    [Patent document 7]    WO2003/77857    [Patent document 8]    PCT/JP 03/10212
Under the above circumstance, the development of a novel integrase inhibitor has been desired.